Vacuum-breaker



,3. W000. VACUUM BREAKER. APPLICATION FILED JUNE 2 19 15- RENEWEJ) FEB. 12, 1921. 1

1,891,600. BatentedSept. 20,1921;

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.UNITED gs'rAres PAT NT OFFICE.

ROBERT woon, on NEW YORK, N. Y.

VACUUM-BREAKER;

To all whom it may concern Be it known that I,'R0BERT WOOD, a-sub-' 'ect of the King of England, and resident of ew York city, in the county of Kings and State of New York, have invented certain new and useful Improvements in Vacuum- Breakers, of which the following is a specification. Y

My invention relates to vacuum breakers or relief valves for steam engine cylinders, particularly locomotive cylinders, and it has for its object to provide a device of this character which will operate automatically to supply a predetermined low steam pressure to the cylinder and prevent the forma tion of a partial vacuum in the cylinder when the steam supply-is cut off or reduced below a certain point.

. In a locomotive the exhaust from the cylinders is usually connected to the "smoke stack to furnish a suction draft for the fire box when desired,-and therefore if a suction is developed in the cylinder it may draw cinders, dust, etc., through the exhaust ports into the cylinder to score the piston and the cylinder walls. T o prevent this entirely the device must operate to prevent the formation of a partial vacuum rather than be operated by a partial vacuum.

With low pressure locomotive it has been customary to equip each cylinder or steam chest with a puppetv valve adapted to open and admit air-in. response. to a suction in the cylinder, but this form of relief valve is objectionable with any locomotive because dirt is liable to enter the cylinder even-though the entrance is screened. For a superheatedsteam locomotive this form of valve has the I further objection that'the admission of cold air to thecylinders causesa deposit of carbon to form on the piston and the cylinder walls. Finally, this form of valve is objectionable because it interferes with modernalubrica tionmethods.

By my invention 'I automatically furnish a predetermined'su'p'ply of steam to thecyl inder'when the throttle is closed and before any: objectionable vacuum can be created in v Specification of Letters Patent Patented S pt 20 1921 Application filed June 2, 1915, Serial No. 31,641.

Renewed February 12, 1921. Serial No. 444,535.

means for opening said valve by the steam pressure from the boiler whenever the pressure 1n the cylinder falls below a certain point and before any vacuum is created in the cylinder.

ltIore specifically, it consists of a differential plston valve controlling this independent passage from the boiler to the cylinder, the-small area end of the piston valve being'always exposed to the full boiler pres-- sure, and the large areaendof the piston valve being always exposed to the pressure in the cylinder, so thatby proportioning the relative areas of the two ends of the differentialpiston valve it may be given an automatic'movement to admit steam from the independent passage to the cylinder'tor cylnders'whenever and as soon as the'pressure 1n the cylinder falls below a given point.

Referring to the accompanying drawlngs: l

of one side of a locomotive showing a preferredembodiment of my invention mounted throttle valve'iI-rthe'engineers cabin as is usual with devices of thischaracter.

i Mounted on one I side of the locomotive relatively closeto the steam chest is a vacu-- um breaker 6 in the form of a tubular block; or casing,provided1 with an attaching Figurel is a diagrammatic outline view plate fllipreferably formed of anintegral casting. I

:Within this casing is a pairof tandem concentric cylinders 8 and 9, the latter'being relatively larger in diameter than the former The outer end of the larger cylinder is closed by a cylinder head or cap 10, and the'inner end 'of the larger cylinder is infree communication with'the adjacent end of the smaller cylinder. The opposite end of" the smaller cylinder is connected by means of a pipe 11 with the locomotive boiler. 7

Within the cylinder 8 there is a snug fitting piston 12, and within the large cylinder 9 there is a snug fitting piston 13. These two pistons may be integral, but for the purpose of avoiding the necessity ofaccurately linin up the walls of the two' cylinders relatively to each other, I prefer to make them separate.

At the head end of the cylinder 9 there is a port14: communicating through a passageway or space 14',-and pipe15 with the steam chest or main steam inlet pipe 16. The cylinder head 10 is arranged to act as a stop to prevent the large piston 13 from closing the port 14, and in order to maintain the piston area substantially the same when it is in contactwith the stop as it is when moved away from the stop, the cylinder head is brought down to a cylindrical knife' edge 17, and ports 18 through the head admit steam pressure to the portion of the piston inclosed within the knife edge when the ports,

piston is in contact-therewith. Obviously the same result may be accomplished by breaks in the knife edge to constitute the 1It will ment Ihave a differential piston in wh ch the small area piston is always subject to boiler pressure, while the large area piston V is always subject to steam chest pressure.

If, therefore, we assume that the areas of these pistons are as ten to one, it will be seen that at all times when the steam chest pressure exceeds'one-tenth ofthe boiler pres sure, both pistons will be forced to their extreme position away from the stop, but that whenever the steam' chest pressure drops 7 below one-tenth of the boiler pressure, the

pistons will be moved into the position shown in Fig.2 with the large piston forced against the stop. Inthe-small cylinder there is a port 19 adapted to be uncovered when the pistons are in the position shown in the drawing,

- and to be closed when thepistons are at or near their other extreme position; The port 19 communicates through a pipe 20with the steam chest or main steam inlet 16. Obviously, therefore, if the pistons are in the position shown in thedrawing, boiler pressure from the pipe 11 passes through the port 19' and the pipe 20 to. the main steam inlet.

Inasmuch as these pistons are not provided with rings or packing of'any' kind, it would be possible for the steam to leak by the piston into the'oylinder space'between the two pistons, and to avoid the accumula tion of pressure in this space, I provide drip passages 21, 22 and 23. The passages 21 and 22 are'both in thetlarge cylinder, and are iesigned to be covered successively by the be observed that by this arrange large piston as it moves away from the stop.

While one ofthese drip passa es would be sufficient for the purpose, I prefler to provide two or more, as they permit the utilization A As a further cushion for the large piston,-

I provide a coil spring24. It will be noted that the spring 24 also tends to maintain.

1permitjthe flow;

thelvalve 12 in position to from pipe 11 into pipe 20 t rough port-19.

The drip 23 serves to prevent the accumula tion of pressure due to leakage whenthe drips 21 and 22 are closed by the large piston, and to increase its facility ofaction' I may provide a groove 25 in the small piston adapted to register with the drip 23 when the pistons are in their extre e position away from the stop. r

r The operation of my device is as follows:

When the engine is running under pressure the small piston is subject to the boiler pressure of say two hundred pounds through the pipe 11. The large piston is subject to sub stantially the same pressure through the i A pipe 15 and the port 14. This will cause the differential pistonv to move to its extreme position away from the stop, .and'conse quently the small piston will port 19.. r

If, however, the engineer closes his throt-,

tle, the steam pressure in the main'inlet pipe 16 and in the steam chest will rapidly fall, and'this will cause substantially the same drop in pressure in the pipe'15" and the port 14. Again assuming that "the piston areas are as ten to one, theposition of the piston will remain unchanged until the steam chest pressure drops below twenty pounds. result will bethat-the constant or boiler pressure on the small piston, will overcome a the pressure on the large piston,- and the differential piston will move towarditsf stop to open the port 19; p 7

As soon as the port19 is'open, the con stantor boiler pressure is: admitted-to the pipe 20, and thence to the main steam inlet and steam chest, whereupon the pressure upon the large piston will rapidly rise. As

close the The soon as this pressure rises above'twenty pounds, the differential p iston w'ill move back to close the port '19, and thereby pref.

vent the pressure from exceedingthe predetermined amount. As-long, therefore, as

the throttle remains closed, this differential pistoniwill float back and-forth't'o maintain a'pressure of substantially 'twenty pounds in the steam chest, thereby preventlng the'for mation of -a partial vicuumin the cylinder. 1 It {is customary in locomotives; to'branch the main steam line to the steam chests on each side ofthe cylinder, and thereforewhen pipe 20 communicating directly with the branch of the steam chest on the other side of the locomotive. a

When the locomotive is coasting, the differential piston floats back and forth to maintain the steam pressure in the. steam chest Within the desired limits, but when the locomotive is standing still with the throttle necessarily tight shut, the differential piston will remain in position away from the stop. Under these circumstances, the provision of drip passages is important, because there might be 'a gradual accumulation of pressure in the steam chest and in the cylinder due to leaka e past the differential piston which wil eventually be sufficient to start the locomotive. For ordinary purposes I have found that the provision of the drips is suflicient, but as an extra precaution I may provide a valve in the pipe 11 to be closed when the engine goes into the round house, or whenever it is desirable.

It will be observed that by this'construction I prevent the formation of a vacuum in the cylinder when the throttle is closed, furnish steam to carryon lubrication, and avoid the admission of cold air to the cylinder. It will also be observed that the device works automatically whenever the pipe 20 is connected with the boiler.

In using the term cylinder injthe claim, I

chest. and the steam inlet.

Having thus described my invention, I

claim:

In a device of the class described, a casing provided with a bore extending therethrough from end to end and substantially closed from the external atmosphere, one end of said bore being enlarged to form the same into alarge chamber and a relatively small chamber, the end of the bore at the small chamber constituting an opening from a source of relatively high pressure, said casing provided with an outlet port leading from the small chamber and adapted to com municate with a space designed normally to have a high working pressure therein, a relatively small piston having a sliding fit in the small chamber and projecting therefrom into the large chamber, said outlet port controlled by said small piston, a relatively large iston having a sliding fit in the large cham er, said pistons coacting to constitute a two-part difi'erential" piston, a

spring acting on the small piston for maintaining the same in bearing engagement with the large piston and for moving said small valve into position uncovering said outlet port, said large chamber provided with a port for placing the large end of the difi'erential piston continuously in open communicationwith said high pressure space and a sto cap for the large end of the bore.

igned at New York, in the county of New York, and State of New York, this 27th day of May, A. D. 1915.

ROBERT WOOD. 

